alert tcp-pkt $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE PackClient RAT CnC Checkin M1"; flow:established,to_server; app-layer-protocol:!tls; xbits:set,ET.PackClient_RAT,track ip_pair,expire 300; dsize:<100; content:"|24 00 40 5a|"; fast_pattern; reference:md5,c55f9bc3c53ac32e6169ad3cc8b2ce49; classtype:trojan-activity; sid:2069878; rev:3; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, affected_product Windows_11, attack_target Client_Endpoint, tls_state plaintext, created_at 2026_06_10, deployment Perimeter, malware_family PackClient_RAT, performance_impact Low, confidence High, signature_severity Major, tag RAT, updated_at 2026_10_14; target:src_ip;)